A freind of mine has one and he flew it all last summer with a TT46, and it flies great with this engine. I would go with the Irvine 53 2 stroke, or a 80 size 4 stroke, either would be awesome on this plane, maybe a 91 4 stroker too, might be a bit much though.
If your looking for a good 4 stoke 91 for $200.00 go with the Saito, or even magnum. I would recommend the Thundertiger, but it has a few more ounces of weight which you dont really need on that plane.
The plane builds up nicely, with no real modifications needed. You might want to change your pushrods to fiberglass, other than that it is a good little bird. Daz...